Recently, the following are done for the cancer therapy: surgical therapy, radiotherapy, and chemotherapy. The chemotherapy is conventionally done by administering to the patients agents which directly act on tumor cells and then kill them. Lots of anti-tumor agents which can be used in the chemotherapy have been known. Since the agents used in the conventional chemotherapy not only kill the tumor cells but act on the normal cells, it has been the problem that the agents have very strong side effects, although they have an high treatment efficiency to the cancers.
It is known that capsaicin (8-methyl-N-vanillyl-6-nonenamide), which is a hot ingredient of red pepper widely used as a spice, has a strong hot taste and preferable effects to a living organism such as appetitive promotion, vascular dilatation, vasoconstriction, enhancement of energy metabolism, and release promotion of biologically active peptides. Recently, the anti-tumor effects of capsaicin has been reported in addition to these preferable physiological effects (D. J. Morre et. al., Proc. Natl. Acad. Sci., 92, 1831–1835 (1995), and K. Takahata et. al, Life Science, 64, PL 165–171 (1999)). Namely, capsaicin has a proliferative inhibitory effect in a low concentration to Hela cell derived from a human (uterocervica cancer cell) and HL-60 cell (acute promyelocytic leukemia cell). However, although capsaicin induces apoptosis-like changes such as nuclear segmentation and agglutination to many survived cells, it has been found that capsaicin specifically acts on the tumor cells without any proliferative inhibitory effects to normal cells of human mammary gland epithelium and of liver and kidney of the rat (D. J. Morre et. al., Proc. Natl. Acad. Sci., 92, 1831–1835 (1995)). As a result, capsaicin has been expected to become an efficient anti-tumor agent with low side effects.
To the contrary, capsaicin is difficult to use as a pharmaceutical agent because of its hot taste, stimulus and inflammation induction, and its continuous administration is stressful to the patients.